Electromagnetic relay



June 21, 1949. E w 2,473,982

' ELECTROMAGNETIC RELAY Filed Nov. 23, 1945 FIG. 2 F|G.3 56 n o m y it I I FlG.6 FIG.8

F|G.7 no.9

Has H63 62 so) so) FIG.|2

42 4 INV TOR. FREDRIO aw 43 4| ATTORNEY Patented June 21, 1949 UNITED PATENT O E 2473,982 ELECTROMAGNETIC RELAY Fredric Wood, Qak Park, Ill., assignor to Automatic ElectricLaboratories, Inc., Chicago, 11]., a corporation of Delaware Application November 23, 1945, Serial No. 630,421

The present invention relates in generalto multi-contact relay switching devices and more particularly to the switching contact spring assembly controlled by the armature of an electromagnetic relay.

It is the -main object of the present invention toprovide an improved twin contact spring assembly for use on'relays, such as commonly used in telephone or like systems.

When designinga twin contact spring assembly for a relay, it is necessary, in order to secure the best results, to have the-two contacts of aspring close with approximatelyequal pressure toassure true twin contact action. This is most readily accomplished by having themovable springs and thestationary springs similar in shape and placed in superposed'relation one above the other as is done in nearly-all known commercial relays. When this practice is deviated. from by placing the main body portion of one spring to, the "side of, or in non-superposed relation to, the main body portion of itsv adjacent spring in order to provide sufficient space to permit easy. manual tensioning of the springs and proper position gauging of the contacts, then a contact extension arm is required on the free end of either one or bothof the springs to properly align thecooperating contacts of the movable and stationary springs. Inthis case When the movable spring engages the contact extension arm of the sta- '-tionary spring a torque action occurs, and in.case

.the contact extension arm has twin contacts thereon then one contact hasheavycontact pres sure and the other twin contact;ha s light;contact pressure or none at all, thus defeatingthemainobjective in-a twin contact design.

One of the features of the invention is to pro.- vide-a twin contact spring assemblyhaving adjacent springs placed in nonesuperposed relation to permit easy adjustment and in which two in- ,jdependen'tly ,flexible contact carrying arms extend from the free end of the stationary spring to align the twin contacts ,on the stationary spring with the contacts ,on the contact carry- .ing branches .of the movable spring, such independently flexible contact car rying arms of the stationary spring being designed to absorb the torque above mentioned and to give equal resistance to movement sons to equalize the contact pressure on the contacts on-the branches of the movable spring. The movable spring also has twoindependently fiexiblebranches-ifor car- .rying the twin contacts of the movable spring so that if :one of thetwo contacts engages before .the other then the other-flexible branch-flexes I.

independent of the first -one to cause the second contact to engage its-associated'working contact.

In combination with the above the movable springs are each provided with a semi rounded hash n ecu ed z eath .cq ta ca ying I 3 Claims.

branches on the longitudinal center line of the movable spring so that each contact carrying branch of each movablespringcan move,lor flex, independent of the other branch in case a first one of the contactspn one of the contact carrying branches engages a contact on one of the arms of a stationary spring before the other contact on the other contact carrying branch engages a contact on the other arm of the stationary spring to assist in equalizing contact pressure and insure twin contactclosure.

It is well known that when the relay armature is attracted .to the relay core, the movable spring contacts strike the contacts of the stationary spring asharp blow thereby causingthe springs to vibrate at a frequency determined by-its length andmass and with an amplitude determined by the striking force.- The effect of the vibrations depends upon their amplitude, which may be enough to separateythe, contacts two or more times before the vibrations die out and the contacts remain closed thereby producing open circuit periods of short durations, These open circuit periods, 'known. as contact-bounce ,or .re-

; lay chatter, often cause false operations which may be of a serious nature and should be eliminated or reduced to a point (in which they are negligible.

Another feature of the present invention provides a simple and effective means for eliminating or reducing open circuit conditions due to contact-bounce to a negligible factor in the previously described improved twin contact spring assembly by extending the clamping base portion of only thestationary spring so as ;to provide a relatively short stiff portion extending from the clamping base and which short stiff portion has two independently flexible S-shaped arms extending from the free end. thereof to align the contacts on such arms with the contacts onthe movablewspring. The'two flexible arms are independently flexible with respect to eachother and togthe short'stiff portion of the stationary spring andare ofdifierentlength and so to have. different periodicities of vibrations and different "amplitudes. Due to the extended clamping means for each stationary spring, the distanceafrom the free .end of the stationary springto the clamping ;baseqis considerably shorter than 'thecorresponding portionpf the movablefispring thereby providing a relatively short stiif'portion -having a different vibratory characteristicthan thelongerand more flexiblernovablespring. "In the stationary spring the distance. from :the clampin base to its free endis relatively short with, the' result .that the stationary spring asga whole will vibrate at a relatively high frequency having a relatively sma emnlitu ethembv cin h pen z r- Qui t cnsi qnse faste in sx rsm-el sh rt durations of time. As previously described the twin contact carrying arms on the free end of the stationary spring are different in length and mass and therefore have different frequencies of vibration and amplitude when struck by the movable spring. During the vibratory periods of these twin contact arms on the stationary spring, one of the pair of twin contacts on one of the arms will vibrate at one frequency and amplitude while the other twin contact on the other arm will vibrate at a different frequency and amplitude, such two difierent frequencies being superimposed on the short stiff portion which vibrates at a third difierent frequency. The main body portion of the movable spring also vibrates at a frequency different from the short stiff portion of the stationary spring and the contact carrying branches of the movable spring vibrate in unison but at a different frequency than the main-body portion. Due to the different vibratory characteristics of the twin arms, the short stiff portion of the stationary spring, the main body portion of the movable spring and the contact carrying branches, none of which vibrate in synchronism, one of the twin contacts on one of the arms may be in engagement with its working contact on the corresponding contact carrying branch of the movable spring while the other twin contact on the other arm of the stationary spring may be out of engagement with its working contact on the other corresponding contact carrying branch of the movable spring so as to maintain the circuit closed through at least one of the twin contacts, thereby reducing or eliminating open circuit conditions.

The invention will be more readily understood from the following detailed description taken in connection with the accompanying drawings in which:

Fig. 1 is a top or plan view of a relay having the improved spring assembly;

Fig. 2 is a side view of the relay shown in Fig. 1;

Fig. 3 is a top or plan view of a similar relay having a slightly modified improved spring assembly;

Fig. 4 is a side view of the relay shown in Fig. 3;

Fig. 5 shows an enlarged top view of one of the stationary springs;

Figs. 6 and Lshow partial top and side views,

respectively, of the extremity of the free ends of the movable springs provided in the spring assembly shown in Figs. 3 and 4;

Figs. 8 and 9 show partial top and side views, respectively, of the extremity of the free ends of the movable springs provided in the spring assembly shown in Figs. 1 and 2 Figs. 10 and 11 show partial top and side views, respectively, of a portion of the make-beforebreak spring shown in Figs. 1 and 2; and

Figs. 12 and 13 show top and end views, respectively, of the insulators used for separating the springs in the spring assemblies.

Referring now more particularly to Figs. 1 and 2 of the drawing, the electromagnetic relay comprises the usual field structure comprising the core 23, winding 25, the L-shaped heel piece 22 secured to the core 23 by means of screw 2| and the armature 26 which is pivotally secured to the heel piece 22 by means of the pivot pin 29, yoke 3| and screw 28. A bronze plate 32 is clamped between the yoke 3| and heel piece 22. The armature 26 has a welded residual 21 to prevent the residual magnetism from maintaining the armature attracted after the winding 25 is deenergized. The armature has a turned over end 30 for engaging the semi-rounded bushing 53 secured to the first movable spring 60 in the spring assembly.

The spring assembly comprises a plurality of insulators 40, stationary springs 50 and movable springs 60 and '10 secured to the heel piece 22 by means of screws and metal top plates 45 as shown in the drawings.

Each stationary spring comprises a terminal end 56, a clamping base portion 51 provided with holes 55, a main body portion 59, S-shaped arms 54 and 55 with an S-shaped slot 53 between such arms, and a contact on each arm as shown in Fig. 5.

Each movable spring has a similar terminal end and clamping base portion also provided with holes, a main bod portion 69, a semirounded bushing 53 secured on the longitudinal center line or" the main body portion, two diverging contact carrying branches 6! and a contact 62 on each of the branches.

The base portions of the stationary springs 55 and the base portions of the movable springs 60 are assembled in superposed relation with an insulator 4Q separating adjacent springs. The main body portions 59 of the stationary springs are assembled in superposed relation, the sim ilar main body portions of the movable springs are also assembled in superposed relation but the main body portions 59 of the stationary springs are assembled in non-superposed relation to said similar main body portions of said movable springs, thereby aligning the main body portions of said movable and stationary springs in different parallel planes.

The insulators 40 are substantially L-shaped and each comprise a main base portion 441 and an extension 4!. Holes 43 are provided in the base portions 4t through which the screws 46 extend to secure the spring assembly to the heel piece. The insulators 40 have embossed lugs 42 which fit into the holes, such as holes 55' of the stationary and movable springs to properly align the same. The extensions 45 are approximately one-half the overall length of the insulators and are provided to extend along onl the main body portions 59 of the stationary springs so as to shorten the free end of each stationary springs so that its free end is approximatciy one-half the length the free ends of the movable springs. Each stationary spring 5E has its base portion 51 and part of its main body portion 59 clamped in the assembly to provide a relatively short stiff free end portion. Since the free ends of the stationary springs are relatively short and stiff as compared to the longer free ends of the movable springs, the free ends of the stationary springs have a natural frequency of vibration difierent from that of the longer free ends of the movable springs.

The S-shaped arms 5 and 55 are of unequal length and mass and are independently flexible with regard to the main bod portion 59. Since the S-shaped arms are of unequal length and mass these two arms each have diiierent frequencies of vibration with respect to each other and the main body portion 59. It should also be noted that the S-shaped arm 54, where it joins the main body portion, is considerably wider than the width of arm 55 where it joins 59. This difference in width of the two arms 54 and 55 has been carefully designed and tested to give equal f resistance to movement so as to equalize'econtact pressure when the contacts F621 of the -movable springs engage. the' c'ontacts "'52 on arms- 54 and 55 -'f'lthe ':movable springs 65) have .cliv'erging' .ter-linejof the mainibodyportion fiil near the;ex-

tremity of the free endof the movable springs. The insulating memberof bushing til-has a semirounded' surface sothatsthe free end/G9 may roclc incase' oneof the contactsrB'Z engages a' contact on'one of the S-shaped arms 54 or 55ibefore the other contact :62 engages a corresponding con- .tact. The diverging branches iii are each in .dependently flexible and are designed to give equal resistance to contact pressure.

The uppermost spring'i'lil is bent near its irec iendtoform aunake-beiore-break spring combination with its Working movable spring Giiand its working stationary spring '50. The main'bcdy portion-:79 of spring 19 isassembled in superposed relation with the main body portions v69 of the movable springs so;asto alignthe spring in the same planeas the main body portionsiiil of the movable springs. Branches H converge from ;the main bodyportion l9 andeachbranch H has a pair 'of contacts 12, one of which cooperates with'a contact 52on'a stationary spring'and the other which cooperates with a contact '52 one .movable spring. Spring It also has. an extension .13 which is clamped between "two extensions -.4l of ,twoc-insulators 4t. Each-movable spring also has: anextensioni similar toextension 'w and these extensions =;are clamped in superposed relation -with the extensions .4ion insulators ill when the spring setis assembled.

Therelay;shownginFigs. Sand 4-is similar in construction to the relayshown :inFigs. land 2 lWithr'SHght modifications. Thearmature 96 has a shorter. arm and the Well known :type ofscrew residual -81. The spring.- assernbly has the same (type of stationary springs, suchas stationary spring 50,;but a slightly different movable'spring 80. .The-.movable springs "Bil; shown in :part-in ,Figs..6 and'7, have a base-portion; similarto the base portion "51; a :main .body portion -'89,'-an extension similar to extension "'63, twc diverging branches "8! which carry the contacts 82,-anrl:a :similar bushing -83 [welded on the longitudinal center-line of--..the-mainsbod --portien 89 -at-the extreme free 1 end of each spring. The-"diverging branches 8| and the convergi-ngportionsformw-a :ClOSEBd. slot Bland these branches 8! are independently flexible and are designed :to; give equal resistance .to movement so as to equalize contact .11

pressure. Insulators -AB alsowseparate adjacent springsin the same -:manner :asdescribedfor .Figs. .1-andr2 -to assemblethefree ends 55 cf the :stationary springs in non-superposed relationto therfreeends 8!! of them-ovable-springs.

Having 1 described the. construction and assembly ofithe relay,-=a-nd1pasticularly the improved cantilever contact spring assembly, the utility and purpose of theinvention will be set forth to en able the invention to .be more and appreciated.

As is well known, it is desirable to confine a relay mounting:space to as'small a space as is possible and, therefore, therelays should be made largesenough to perform the irequiredifunctions 75 fully understood '70 6 and no larger. *Imdesigning contact-1springvas- 'se'mblies' for e1ectromagnetic--relays it is desirable to" confine-the spring assemblies within a certain limit which does not exceed the overall width of the ima'gneticstructure of .the relay. The usual method .is tto assemble? both". the movable springs and the 'stationary springs in-superposed relartion one .-over therother, and; iii? a large number of switching contacts is-desired, to provide the :relay i-with'itwo" armature arms and two sets' -of spring t-assemblies, each operated :byits corresponding anmaturearm. In spring assemblies: of ithis rtypeeadjacent-springs are usually too?v close to permit easy access for the required adiust- -ments, such :asrtensioni-ng the springs and proper position gaugingwof'the contacts. Such adjustz-ments are .manuallyperformed*by duck bill pliers or special-tools :and if sufficient space is not-proavided for these tools-proper adjustments cannot 120 *be made. The preferred method to overcome ithis diffi'culty is "to 'assemble'themovable' portions of the, stationary springs in non-superposed :rela- -tion .wi-ththe' movable portions i of the movable springs thereby. providing. suflicient space between similar stationary'andsimilar' movable springs.

When the movable'portions,.or main bodyportions 59, of the stationary springs'fifl are as- 'sembled fin non-superposed relation with the amovablewportions, or --main :body portions 2 B 91 or 289 iof the movable springs 60 I or 180, :exten'sion con- .-tact carrying arms or contact carrying branches are} neededztolproperly align theworki-ngcontacts. IT-heiengagement 1 of the contacts on these extenssion :armsand branches; causes atorque action in oneorbothsprings and incase twin contacts are used on.the.armsandabranches-one of the contacts twill have .heavycontact pressure andthe other twin contact willv have light contact pressure or none at. all. unless -some arrangement .is provided 1:4 gto .overcome this defect. -,In order to .provide equalization of. contactpressure on thetwin con- ,tacts thesprings areprovided with'independen-tly [flexible contact carrying arms and .branches so that. they ,may .fiex independently: of each other.

The contact carryingbranches, suchas 6 I- and8l,

15 on such arms'with'the cooperating con'tactson the-bra-nches of the-corrspondinggmovable spring. i ls willloe noted the S-shaped arm '54 islonger :a-nd wid'erthan the ,S-shaped arm in order togive e'qual resistanceto movement and to overcome" the --torque action previously referred to.

The twin-contactcarrying arms 54 and 55 of the stationary springs and "the contact carrying --branches 6I,--or-8l, of movable springs and'8.0 -:are 'purposedly.designedto give true "twin conitact action and'equalization of contact pressure. *"mhe s-zshapedarms 54 and 55 and the contact vcarryi-ng :branches 5 I and '8 I are independently flexible and oilenequal resistance to-movement so'that if i one" pair of cooperating contacts should 5 :engage beforetheother pair of cooperating con- :tacts",-:then the branch'carrying the other contact will be flexed while-thefirstlbranch will be held ate. cause :the otherpair of cooperating contacts i engageythus-insuring twin circuit closures. 'I heisemi-rounded bushings "Band 83 assist in insuring twin contact closures by permitting one branch atoifiexvmorethan the-other, if the other is .in' ien'gagement with its associated working :cont-act.

Practically all contact spring=assemblies"have what is known as contact-bounce or relay chatter. This contact-bounce or chatter is caused by the movable contacts striking the stationary contacts a sharp blow thereby causing the springs carrying such contacts to vibrate at a frequency determined by its length and mass and with an amplitude determined by the striking force. The amplitude of these vibrations may be enough to separate the contacts two or more times before the vibrations die out. These conditions produce open circuit periods of short durations which often cause false operations which may be of a serious nature and should be eliminated if possible.

In the present invention the open circuit conditions, due to contact-bounce, have been entirely eliminated or have been reduced to a point where they no longer cause false operations. As will be noted the extensions 4| of the insulators 40 have been extended along only the main body portions 59 of the stationary spring 50 so that the movable portion, or free end, of the stationary spring comprises a relatively short stiff portion considerably shorter than the movable portion, or main body portions 69 or 89, of the movable springs 60 and 80. The short stiff portion of each stationary spring therefore has higher vibratory characteristics than the longer and more flexible movable springs. The free end of the stationary spring, as a whole, since it is short and stiff, will vibrate at a relatively high frequency and small amplitude thereby reducing the open circuit conditions to extremely short durations of time. The S-shaped arms 54 and 55 are of unequal length and mass and therefore have different frequencies of vibration and amplitude when struck by the movable spring and therefore vibrate at different frequencies. During the vibratory periods of the S-shaped arms and the free end of the stationary spring, one of the pair of twin contacts 52 on one of the arms will vibrate at one frequency and amplitude, the other twin contact on the other arm will vibrate at a different frequency while the short stiff portion will vibrate at a still different frequency. The main body portion of the movable spring also vibrates at a still different frequency while the contact carrying branches such as 6| or 81 vibrate in unison but at a frequency different than the frequency of the main body portion. Since none of these frequencies are in synchronism, one of the twin contacts on one of the S-shaped arms may be in engagement with its working contact on the corresponding contact carrying branch of the movable spring while the other twin contact on the other S-shaped arm of the stationary spring may be out of engagement with its working contact on the other corresponding contact carrying branch of the movable spring, so as to maintain the circuit closed through at least one of the twin contact pairs thereby eliminating or reducing open circuit conditions.

With all the above mentioned features combined in one rela it has been found that, with this spring assembly properly adjusted, and with the relay operating at a speed required in telephone systems, which does not exceed thirty-five pulses per second, that open circuit conditions caused by contact-bounce ar entirely eliminated.

Having described the invention, what is considered new and desired to have protected by Letters Patent is specifically pointed out in the following claims.

What is claimed is:

1. In a twin contact cantilever spring assembly comprising movable springs and stationary springs of approximately the same overall ls .gth, each said spring having a clamping base portion and a free end extending endwise therefrom, means for clamping said base portions of said springs in superposed relation with the free ends of said stationary springs in one plane and with the free ends of said movable springs in a different plane, said clamping means including an L- shaped insulator separating said base portions, an extension on each insulator being approximately one-half that of the overall length of such insulator and extending endwise in only the same plane as the free ends of said stationary springs to reduce the length of the free ends of said stationary springs to that of approximately one-half that of the movable springs, said movable and stationar springs thereby having long and short flexing lengths, respectively, and are confined within a space extending endwise from and no wider than said clamping means to reduce the mounting space required for said springs, a pair of diverging branches on each movable spring near the extremity of its free end, a contact on each branch, 2. pair of S-shaped arms on each stationary spring near the extremity of its free end, each S-shaped arm extending from said one plane into the movable path of and into said different plane of said branches of the free ends of said movable springs, and a contact on each cooperating with a contact on a corresponding branch.

In a twin contact spring assembly comprising movable and stationary springs having common base portions and flexing portions extending endwise from said base portions, said base portions of said springs being arranged in superposed relation and the flexing portions of said movable springs being arranged in non-superposed relation with the flexing portions of said stationary springs, L-shaped insulators for separating and clamping said common base portions of all said springs to permit flexing of said movable springs the entire length of their flexing portions, an extension on each insulator extending endwise therefrom for clamping a portion of the flexing portion of said stationary springs to thereby shorten the flexing length of said stationary springs, said flexing portions of all said springs being confined within a spac extending endwise from and no wider than said insulators to reduce the mounting space required for said springs, and S-shaped arms having contacts on each stationary spring for cooperation with corresponding contacts on said movable springs.

3. A twin contact spring assembly as claimed in claim 2 including an additional extension arm extending endwise from said common base portions of said movable springs and arranged in superposed relation with the clamped flexible portions of said stationary springs to build up an effective clamping means to permit flexing of only that portion of the stationary springs which extend endwise from said insulator extensions.

FREDRIC E. WOOD.

REFERENCES CITED UNITED STATES PATENTS Name Date Wood Apr. 2, 1946 Number 

